


Berkelium

by 7PercentSolution



Series: Periodic Tales [12]
Category: Sherlock (TV)
Genre: Angst, Autistic Sherlock, Big Brother Mycroft, Chemistry, Childhood Trauma, Gen, Homelessness, Missing Persons, abelist prejudice
Language: English
Status: Completed
Published: 2016-09-02
Updated: 2016-09-12
Packaged: 2018-08-12 14:52:15
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 18,500
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7938739
Author URL: https://archiveofourown.org/users/7PercentSolution/pseuds/7PercentSolution
Summary: <blockquote class="userstuff">
              <p>Berkelium was first produced in 1949 at the University of California, Berkeley, for which it is named. A silvery-white highly radioactive metal, Berkelium is produced in miniscule amounts in nuclear reactors by nuclear bombardment of plutonium, curium or americium with alpha particles. It is of scientific research interest only, being used extensively in the hunt to find the higher, as yet unverified heavyweight of the periodic table- 117. The search has proved very, very difficult, involving hundreds of scientists for more than ten years with no end in sight. Sherlock understands that in a way few people can.</p>
            </blockquote>





	1. Chapter 1

**Author's Note:**

> "Sometimes it is what you discover in the search itself that is the most important thing." Sherlock speaks from experience- in more ways than one.

**Berkelium 97 247 (Part One)**

 

* * *

John was passing the table where Sherlock had been sitting for most of the morning. He looked over the taller man's shoulder at the laptop screen, curious to know what had absorbed all of his flatmate's concentration for the past two and a half hours since breakfast. There was a pad of paper next to the laptop, which was now filled with odd symbols, mathematical calculations and doodles. Sherlock was still in his pyjamas and dressing gown, attention riveted to the screen.

"Um, Sherlock- is that Japanese you're reading?"

"Yes." He didn't raise his eyes.

"Why?"

"Because that is the language spoken at the RIKEN Nishina Center for Accelerator-Based Science."

John rolled his eyes and muttered, "Why didn't I know that?" Sherlock smirked and started to reply, but John beat him to it. "Okay, I'm an idiot for not asking the right question, which is, _WHAT_ are you reading that happens to be in Japanese?"

"I'm studying how the RIKEN scientists sorted out 113."

"One one three… _what_?"

Now it was Sherlock's turn to roll his eyes. "Otherwise known as ununtrium. One hundred and thirteen on the Periodic Table. I want to know if their experience is relevant to the efforts of the Russians and the Americans who are competing to produce ununseptium; that's 117, a superheavy element with an atomic weight of 294. The Japanese physicist now working in the USA was at RIKEN and worked on 113; that may give him a unique perspective. Having gone through the pain of the search himself, he may be better able to succeed on this one."

"Okaay, _now_ I will ask why? Why would you want to know something like that?"

"Because both the Russians and the Americans who have been chasing this mystery for years now claim to have identified six atoms of 117's isotopes 293 and 294 in fusion reactions between Calcium and Berkelium. If it's true, then it's…amazing."

"I'll have to take your word for it." John went into the kitchen and started to make some tea.

"Where's your spirit of adventure, John? This is a hunt for the missing element that has been going on for the past decade. It's amazingly difficult. A bit like finding a needle in an entire galaxy of haystacks."

"For someone who doesn't know the basics about the solar system, why use a galaxy?" John was smirking as he put the teabags into the two mugs.

Sherlock growled, "It's a _metaphor,_ John. Or is your tiny mind unable to appreciate the size differential between the solar system and the galaxy, irrespective of the sun's position relative to the earth in either?"

John filled the mugs with the boiling water, stirred and then extracted the tea bags and added milk. Two teaspoons of sugar into Sherlock's and a vigorous stir. As he came back into the living room, the doctor was still smiling. "Whatever the scale you apply to this search for some odd atoms, I'm curious to know what can possibly keep you entertained about it for hours at a time. On the other hand, I should be grateful, I suppose. At least this doesn't involved explosions, poison or body parts."

Sherlock raised his eyebrows. "Actually, it does involve _explosions_ \- of the sort caused by nuclear reactions. And, being radioactive, it would be _poisonous_ to all _body parts_. But the reason why it is interesting is that it is so very hard to prove when the life of these elements can be as short as a few seconds."

John started to take a sip, then realised it was still too hot. "Then why is it important? What possible difference can it make, if the ..un…un-whatever it is- is that short lived?"

"A life- or indeed a half-life- is not the issue, John. Sometimes it is what you discover in the search itself that is the most important thing."

John was utterly confused now. Physics had never been a subject that remotely interested him at school.

The sound of the flat's doorbell filled the awkward silence. Both men counted the seconds as it was pressed- and drew the same conclusion: "Client!" they said, simultaneously. Sherlock slammed his laptop closed and sprinted down the hallway, calling over his shoulder, "keep them entertained while I get dressed!"

By the time Sherlock reappeared ten minutes later in his customary suit, John had sat the client down and prepared a cup of tea for her. She was an anxious woman in her mid-fifties, whose once attractive face was now lined with worry. Well dressed in expensive clothing, but not wearing makeup or taking any particular care in her grooming, she sat on the hard chair facing his and Sherlock's chair. When John told her that it wouldn't be long, she gave a nervous smile. "That's quite alright. I can wait."

As soon as Sherlock sat down in his chair, she spoke. "Mister Holmes, I'm Abigail Barfoot. I've come to ask for your help in finding someone who has gone missing; my son, Alex, to be precise. He's twenty-one now. He disappeared four years ago. I've done all the obvious things- filed the missing persons report, informed the police and social services, the hospitals, the homeless charities and hostels. I've hired private detectives; they've come up with nothing. We lived in Basingstoke, but every available time- weekends, evenings, holidays, I came up to London and tried to find him. I moved here two years ago to make it easier to search. The police…well, they've been useless. I need _your_ help to find him."

Sherlock gave one of his bored sighs. "Over 100,000 teenagers run away from home every year in the UK. That's one every five minutes. They leave for all sorts of reasons, some of those can be very rational choices. Often they come back or at least get in touch. Sometimes they don't- they choose to make their own lives, away from their families. That's rather… ordinary."

John watched the woman's face crumple, and saw her pain- the accumulation of four years of loss. He wished that Sherlock had not been so blunt. Her hands were twisting in her lap, as if they had a life of their own, and wanted to say what she couldn't. Then she raised her head, and seemed to find some courage from deep within.

"Don't you think I _know_ all that? And, any minute now you're going to say what they all say- the police, the social workers, even the countless homeless people I've talked to over the years- you're going to say that he's not a minor anymore, so it's up to him what he does. _But you're wrong."_

Sherlock actually rolled his eyes, and shifted in his seat, as if getting ready to get up and leave. John was often appalled by the man's social ineptitude, but this was just about as insensitive as he'd ever seen him. The doctor leaned forward as if to forestall Sherlock's departure, and in a gentle voice asked, "Why do you believe Alex is a special case, Mrs. Barfoot?" He shot a stern look at his flatmate, as if with a glance he could pin him to his chair for a moment or two more.

"Alex's father would never allow him to be diagnosed, but I think he is Asperger's." Then she shrugged, "but who knows, I'm not the expert. His dad refused to cut him any slack, was always on at him to 'act normal' and get on with it. When he was at school, Alex got picked on a lot, bullied- but Harry- he's my husband, well, _was_ my husband until we divorced two years ago- he just told Alex to fight back. Sent him off the karate class and paid for him to learn how to defend himself. And, well it worked, the kids left him alone after that and he just got on- went to sixth-form college, was doing art, and seemed okay. But, things went from bad to worse with Harry and they had a big fight- I still don't know what it was about- and then Alex left. I thought at first it was just to, I don't know, get some breathing space for a day or two. But he didn't come back. He didn't take his meds with him; he didn't take anything, apart from the clothes on his back and about enough pocket money to get the bus into London. I know that things will have gone really wrong. He _needed_ his meds; they kept him stable enough to function." She ran out of breath for a moment.

John took his eyes off of Mrs Barfoot and glanced at Sherlock. Then looked more carefully, because Sherlock seemed to have gone very… _still._

The woman started again. "I'm not a fool; I know Alex came to London. And I know what kind of life he could manage here. Lord knows, I've seen enough homeless kids over the past four years- the drugs, the ill-health, sleeping rough, in trouble with the law. And that's for _normal_ kids. I keep hoping- God help me, but I really do- that he will get ill enough to end up in a hospital so I can find him. Every hospital in a fifty mile radius of London has his photo- I even pay someone every year to update it- to make it look like he should look as he gets a year older."

She drew a ragged breath and carried on. "But nothing. Not a single word. Six weeks after he left, I started on the morgues. In case he's moved out, now I've done all around the country- there isn't one police force that doesn't have a photo and my contact details."

The anxious woman stopped for a moment, as if gathering strength. "I've been to three _viewings -_ that's what they call it when they have a body that fits the description and they need someone to identify the victim. Three times I've had to prepare myself to find him dead. It was…awful. Oh yeah," she gave a kind of hysterical laugh, "on the one hand I should be happy it wasn't him, but then even that gets spoiled by the thought that there is some mother, someone who loved that boy, _who doesn't even know he is dead._ " She was trying to stop from crying, but it was a losing battle.

Sherlock had not moved at all throughout her outpouring of grief. His stony face was impassive, his eyes hooded, not looking at Mrs Barfoot or John.

In the awkward silence, John felt compelled to ask a question. "Has there been no contact at all- with friends or relatives, other people he might turn to?"

She bit her lip. "Friends? You must be joking. He didn't have any. And relatives? I'm an only child, and so is Alex. He has a whole slew of aunts, uncles, cousins- the lot- on his father's side, but they were hateful, absolutely horrid to him. The total disinterest from Harry and his family- well, it's the main reason why I divorced him two years ago. His reaction to Alex leaving was 'good riddance to bad rubbish.'"

Sherlock stirred. Finally he said something. "Did you move house, change your telephone number, after the divorce?"

Mrs Barfoot sat back in the chair, as if really seeing Sherlock for the first time. "Oh, she said you were smart."

Sherlock's reply was immediate, "Who?"

"She calls herself Angel. I wouldn't have come to you, but Angel said you might be able to help."

"Describe her to me. I know several Angels."

"This one is in her late-twenties- but looks like a teenager. She's got magenta hair; hangs out in mid-town, sometimes Waterloo. She's one of the few who's not on the game, as far as I can tell."

Sherlock nodded curtly. John knew her from the Homeless Network. She'd once been willing, albeit reluctant, to pass on a message to Raz for John.

Mrs Barfoot took Sherlock's nod as an encouraging sign. "Your question about me moving…yeah, it's been really, really freaking me that if Alex changed his mind and tried to call home- well, both Harry and I left there when we got divorced. He's in the Middle East now, working on some big contract in the Gulf. The phone number's disconnected. I left my contact details at the house, but there's been three families in there since- God knows if he did try to find me, he wouldn't be able to."

Sherlock still wouldn't make anything but the briefest of eye contact with her. He steepled his fingers under his chin. "Why do you want to find him, and why do you think it is important for him to be able to find you?"

For a moment, she seemed startled by the question, but then she gave a small laugh. "Everyone asks the first question, but no one ever asks me the second one. The obvious answer to the first-that I'm his mother and want to know he is alright- is, well… _obvious_. But it isn't really the reason now." She stopped, looking down at the floor and a silence fell. John was beginning to feel uncomfortable and thought of something to say to keep the conversation going, but the slightest of hand gestures from Sherlock caught his eye, and John turned to see the taller man give a tiny shake of his head. So, he let the silence lengthen.

When the woman looked up, there was clarity in her eyes. "It's because he never really got the choice. Alex left because _my husband_ made it impossible for him to stay- or at least that's what it must have felt like. He has no idea that me and Harry have split up. He has no idea that it could be possible to have contact with me again, without all that baggage. I'd like him to have the choice, instead of just allowing what happened back then to just shut off everything."

"Say he made contact- but you didn't …like what you saw. What then?" There was an undercurrent of intensity in Sherlock's question.

But Abigail Barfoot was not intimidated. "I've thought about that a lot. If he wanted my help, I'd give it."

"And if he didn't?"

She nodded slowly. "Well, I'd just have to accept that decision. As long as he gets the chance to make the decision, I can live with it. It's the…not knowing that is so painful."

It was as if she had passed some sort of test. John watched in surprise as Sherlock's whole body language changed. The taller man's position in the chair relaxed, his shoulders softened and he leaned forward to ask, "Tell me what he was _really_ interested in, his passion, his obsession."

That raised the ghost of a smile from Abigail. "Alex loves drawing. He's really good at buildings. I know it's been four years, but I can't imagine him stopping. Couldn't draw faces or people, things that moved; he said they scared him. But a building? Well, he'd spend hours getting every little detail down perfectly."

"Let us see the latest photo."

She reached into her handbag and then handed over the photo. John took it first and looked before handing it onto Sherlock. Alex looked young and rather ordinary- brown straight hair, brown eyes, in a face that looked like…well, a lot of other young men's faces. The image was sort of a hybrid- half way between a normal photo and something that might have been done by a photo-shop expert, willing to turn an ordinary snapshot into something that could be used more professionally. "His height and weight at 17 are on the back, as well as an estimate from his doctor of what he'd be now. Keep it; I've got hundreds more."

She was now sitting on the edge of her seat, hopeful. "Does this mean you will take the case, Mister Holmes?"

Sherlock did not look at her face. He said quietly, "I cannot guarantee to find him. In fact, the odds are seriously stacked against that. There are over eight million people living in London, and by now, if he is still alive, he will have a different identity, which is why no one can find him. It is unlikely that he is still sleeping rough, so his trail will be incredibly difficult to find."

His voice was neutral, careful in tone. "I do not want under any circumstances to mislead you. Anything could have happened. If I do find out what happened, it is quite possible that he's dead."

She nodded. "I know. I've lived with that for four years. If he is, then I can at least lay him to rest in my mind."

"You must be prepared for another possibility. If I do find him alive, he may want nothing to do with you. I will ask him if he wants to make contact. If he does not, then I won't tell you anything other than the fact that he is alive and does not want to see you. If you are prepared to accept those terms, then I will look for him."

She nodded.

"It may take…some considerable time. Do not contact me again, Mrs Barfoot. If I am able to find anything out, I will contact you. Good day." With that somewhat abrupt ending, Sherlock got up and left the room.

It was left to a somewhat startled John to take her details down, and to see her out. He tried to be as reassuring as possible. "Please forgive his manner; he's…well, blunt is a polite way of putting it."

For the first time since she'd come into the flat, Abigail Barfoot smiled broadly. "Oh, you don't have to apologise for him. I know what someone on the Spectrum is like. And, if what Angel said is right, Mister Holmes knows what it is like to be in Alex's place. I hope to God that helps him find my boy."

oOo

"I have good news, Holmes."

Mycroft got up to shake hands with the man who had come into the room and sat down in the leather armchair across from him. Sir Andrew Middleton was a former barrister, a middle-aged QC who had declined the offer of an appointment to the judge's bench. Instead, Sir Andrew had become an unpaid political treasurer, contributing a large amount of time, energy and cash to the Government's party coffers. But that would still have not been enough to earn him the most coveted appointment in the UK's diplomatic service. Her Majesty's Ambassador to the United States was ferociously intelligent and politically astute- a combination that made him ideally suited to deal with the mercurial political in-fighting that characterised the "special relationship." No one in the Foreign Service begrudged Sir Andrew the appointment when it came.

On the surface, however, an outside observer of the meeting would have been puzzled. Despite having the glittering career, the knighthood, the public recognition, the older man was the one who seemed more eager to please. The twenty three year old taking his seat again across from him was an unknown policy analyst, a minor official in the embassy staff, who had been in post for less than seven months whilst working with the White House's National Security Council. But the other thing that Sir Andrew was renowned for was being able to pick winners. And the young man now accepting a cup of tea from the butler was neither intimidated by that fact, nor by the man's obvious patronage. That the younger man was the one in possession of an aristocratic title and the connections that came with it meant that association with him was as beneficial to the older man as the Ambassador's mentoring was helpful to the younger. And they both knew it.

Outside, the late September Indian summer was making the Washington embassy's air conditioning work hard, but the leaves of the trees lining Massachusetts Avenue were starting to take on autumn colour, so it would not be long now before there was some relief. Mind you, after the tropical conditions of Central America, Mycroft had not objected to Washington's three H's – hot, humid and hazy- that characterised its summers. This summer had been particularly interesting. He had been working in the background of the US House Permanent Select Committee on Intelligence. The Congressmen were investigated allegations about illegal CIA involvement in the cocaine trade, as a way of funding counter-revolutionary movements without having to rely on public appropriations.

Sir Andrew took a welcome sip of the Fortnum & Mason's blended tea, and then smiled. "The FCO and the Prime Minister have agreed to the Cabinet Office plan. You're to finish your stint here, and then by Christmas, when the paperwork will be done, the new service can get started." He raised his cup as if it were a glass in a toast, "Here's to the new Security and Intelligence Liaison Service."

Mycroft raised his cup in a mock salute. Tonight he might well open a rather special bottle of Dom Perignon champagne to celebrate properly. It was the end of his career as a foot soldier, a field operative of MI6. Confined by the operational procedures and loathing the restraints that the massive agency's protocols required, he had talked Sir Andrew and his Cabinet Office connections into a brand new approach- a small elite, staffed by only the very brightest of minds, with limited budget and no real field functions. Of course, if asked, they would all swear it was their idea initially, and that Mycroft Holmes had simply helped them think it through. He was useful like that.

The new service would be small, but perfectly formed. It would have access to _every_ agency's work and information. Set above the internecine battles that traditionally made them reluctant to share intelligence, this new SILS would ensure that no one missed anything crucial. And Mycroft would be one of the new appointments, working as the number two in the strategic oversight function. He had only one niggling worry about his appointment- he suspected that there might have been a bit of push for it by someone he would rather not have been involved: FS Ford, whose star in the intelligence firmament seemed to be rising higher every day.** But Mycroft wanted this position enough to look the other way, no matter who was involved. By the time he got back to London, he'd be twenty four years old- an age when most young men would be lucky to be enjoying their first solo field operation. To say that it was a significant promotion would be nothing short of a breath taking understatement. And Mycroft knew it.

"Thank you, Sir Andrew, for all your help. I do appreciate it." This was accompanied by one of Mycroft's social smiles. He was good at that- making people feel special. It was something he had learned by watching his mother do it with the Estate workers. It was remarkably easy to build someone's loyalty and trust.

He was looking forward to returning to England. Mycroft _loathed_ fieldwork. The hostile and distracting environments, the people with whom he had to work, the strain of pretending to be both stupid and obedient enough to follow orders when he knew that there was a better way to actually achieve what his superiors wanted. At last, that era was coming to an end. And being back in England meant he would be able to be more visible at Parham, which would be reassuring to the staff. It had been eleven months since his father died; time to be seen to be taking an interest again.

There was a knock at the door, and Sir Andrew called out, "Enter."

His private secretary came in. "I'm sorry to interrupt, Sir, but there is a phone call for Lord Holmes."

The use of the title set off alarm bells. Mycroft stood and turned to the Ambassador, who spoke first. "Go on- I have to get to the reception at the White House. Are you sure you want to give that a miss? Might have something to celebrate there now."

Mycroft gave a slightly strained smile. "No, thank you; President Clinton insists on serving that New York State sparkling wine that he has the temerity to call champagne." He gave a shudder, and Sir Andrew laughed, adding "Yes, but I do so enjoy watching the French Ambassador go apoplectic as a result." He was still chuckling at his own joke as the two men exited the room.

Mycroft took the call in the Ambassador's office. Some instinct made him seek privacy. "Holmes speaking."

"I'm sorry to disturb you, m'Lord."

"Mrs Walters. What's happened?" It was calmly said, by a young man whose mind was anything but calm. For the Parham Housekeeper to ring him like this was unusual- and more than alarming.

"It's Sherlock. He's disappeared."

For a split second, Mycroft's memory conjured up a similar phone call, seven years ago, when his mother was still alive; Mrs Walters had telephoned him at Eton College to tell him that his nine year old brother had gone missing*. That had ended well enough.

"When? I thought he was supposed to be in Cambridge by now."

"That's just the point. Trinity College telephoned this morning to say that he'd not showed up. They gave him a few days grace, but were calling to say if he wasn't coming, they need to know. You do know, don't you, that Sherlock's been staying these past two weeks with his chemistry master, Robert McGarry? He was supposed to drive him up to Cambridge and get him settled in. He was the one who recommended him to the college, and went with him for the interview. He's been quite good with Sherlock while he was at Harrow."

"I am aware of that, Mrs Walters. What does McGarry say about Sherlock? Does he know where he might have gone?"

There was a moment of hesitation. Then she said quietly. "That's the problem, m'lord. There was no answer when I called his house in Harrow, so I got the school to send someone around to see what was going on, maybe his telephone was out of order or something. Anyway, they went round to his house, and…well, they found him, Mister McGarry. He was dead. The police say it's been a couple of days. There's no sign of a break in; according to them, it looks like he died in his sleep from natural causes."

Mycroft just closed his eyes for a moment, aghast. He tried to imagine what Sherlock would have gone through when discovering the man was dead. When he found his voice again, "Any sign of Sherlock?"

"No sir. His things were all there, packed up ready to go. Three days' worth of newspapers still on the mat, pushed through the letterbox, but no sign of Sherlock. The police are trying to find him."

"Presumably, you've checked at the London townhouse?"

"Of course, sir. I wouldn't bother you before we'd done the obvious things. None of the staff either there or here at Parham got a call. I thought he might have phoned Frank Wallace, but he hasn't. And no one from the school, either. Then I thought he might have tried, you know, to…um…walk home to Parham, given the last time, but the police haven't been able to spot anything on their CCTV cameras, and they think they would have if he'd gone on foot across London to get to us. They say he may have got on a tube train at Harrow on Saturday morning, but there was a football match on at Wembley and the metropolitan line platform was very crowded; they can't be sure."

 _Oh Sherlock, what have you done. Why didn't you call ME?_ But, as soon as he thought that, he knew the answer. Why should his brother bother trying to contact a person who was little more than an overseas address or telephone number? Mycroft knew he had allowed whatever connection had once been there between him and Sherlock to wither. For years, he'd rationalised that this was what his brother wanted. Any overtures on his part had been batted away furiously by a young boy who wanted no part of anyone. "Just leave me alone" was Sherlock's motto; it had certainly been thrown back in Mycroft's face often enough when he was still at Oxford.

As a result, for one of the first times in his life, Mycroft had absolutely no idea what to do. The idea of his little brother being traumatised by the unexpected death of one of the few human beings he was willing to tolerate was bad enough. But, add to that the fact that Sherlock was now lost somewhere in London, not willing to contact anyone, was just horrifying. He knew his brother was resourceful- he'd managed a sixty mile walk across southern England on his own at nine. But the rural byways and back roads were very different from the streets of London. Mycroft's imagination supplied the images of a vulnerable teenager overwhelmed by the sensory stimuli, scared and unable to approach anyone he didn't recognise. This was a boy who once spent seven months mute. Would he be able to speak now, even if he wanted to?

"Mrs Walters, do the police know why they have to treat this seriously?" He tried to suppress the anxiety in his tone.

Even across the Atlantic, he could hear her sigh. "They just keep saying that it happens all the time. Teenagers go missing so often- dozens and dozens every day apparently- and most of them go back when they've cooled off."

"This isn't the same. Sherlock is not some…ordinary hormonal teenager going off in a huff about something silly. He will have been seriously affected by McGarry's death."

"I _know_ that!" he could hear the distress in the older woman's voice. "I've told the case officer about Sherlock but, well, she says it's very early days yet. 'Just wait until the shock's worn off and he will get in touch, or someone will find him'. They don't understand Sherlock; they don't know what he's like…So, m'lord, what do you want us to do?"

Mycroft sagged against the ambassador's desk, and tried to focus. _Think!_ What would Sherlock do? He found it difficult, no…impossible to say. He had spent so much time overseas over the past four years that he hardly knew his brother. The last time they'd met face to face was at their father's funeral, ten months ago. He knew that the Harrow chemistry master had been a formative influence on his brother, if only because of the subject- "the only thing that is bearable in this academic black hole" was how Sherlock had described it in the one letter that had been written to Mycroft during Sherlock's entire three years at Harrow. That letter was after the A level and the Common Entrance Exam results, when Sherlock told him that Trinity would take him. McGarry had taken him to the interview, and he must have been able to coach Sherlock into sounding half-way presentable. That made him almost unique for Sherlock- someone to whom he would listen. The man who was responsible for getting Sherlock to focus on university was now dead. How would that affect his brother's motivations? He hadn't a clue. For all he knew, Sherlock might have thought he had something to do with the man's death. That's when Mycroft realised that he needed a professional's opinion.

"Mrs Walters. I want you to call Doctor Esther Cohen. Tell her what you've told me, and follow her advice. I will be on a plane tonight. I will fax my arrival time- have Stimpson meet me with the car at Heathrow. Once I am back in London, I can start the search." Even as the words left his mouth, he realised how hard it would be. If Sherlock did not want to be found, it would be almost impossible.

* * *

 


	2. Chapter 2

**Summary for the Chapter:**

> Most elements heavier than uranium are highly unstable and nearly impossible to find in nature. Finding increasingly heavier elements involves smashing together lighter elements like Berkelium in the hope of creating islands of stability, a group of short-lived, massive but very briefly stable atoms. Even so, the atoms survive for less than a tenth of a second before decaying into lighter elements. Making this happen is very, very hard. Being able to trace the decay is even harder.

After accepting the case of Alex Barfoot, Sherlock would not discuss it further with John. "I have to do this one myself, John." No matter how the doctor tried to coax the reason why, the consulting detective would not budge.

"Why don't you want me to get involved, Sherlock?" The doctor was somewhat perplexed at his flatmate's insistence on doing this alone.

"Because this one cannot be solved linearly. Because of your training as a doctor and in the army, you think in straight lines, in cause and effects, in sequences. Given the vast amount of possible data out there, the only way this will work is the unlikely collision of two or more bits of information, randomly generated, seemingly unrelated, which come together for the briefest of moments before disappearing."

John tried to imagine what that actually meant. "For example?"

Sherlock sighed. "I can't explain it any other way. I will know it when I see it. The difficult part is being in the right place at the right time to see the collision of data, and to spot what results, no matter how short lived. Sometimes, it's what isn't there that is the more significant fact."

Other cases came and went. There was no evidence that Sherlock was making any progress in finding Alex; in fact, no evidence at all that he was even working on the case. Over the next month, Sherlock spent a little more time than usual with his Homeless Network, but always on his own. John started to forget about the missing youth.

Then, one morning the doorbell rang. After so many times, he'd learned when there was a client on the other end of the buzzer; this was not one of those occasions. As he came down the top flight of stairs from his bedroom, John heard Mrs Hudson talking to someone in the hallway. But by the time he got down to the ground floor it was just as the front door shut rather firmly.

Mrs Hudson was standing in the hall, looking rather perplexed. She had her apron on and had one marigold glove on her left hand. In the other, she was holding something. Even folded, the paper was a good size and firmer, heavier in weight than the sort of paper used in a printer. Not quite poster board, but not normal paper.

"What's that, Mrs Hudson?"

"She just pushed it into my hand and said, 'tell him it's from the King's Cross Shelter- on the manager's office wall. Been there for at least three years', she said."

"Who delivered it?"

"One of Sherlock's…you know… street people. Little thing, couldn't have been over fifteen. All dirty and wouldn't tell me her name. I think she was high."

John gave a rather pained smile. Most of Sherlock's Homeless Network both alarmed and worried Mrs Hudson. Her maternal instincts warred with her sense of cleanliness and proper behaviour. He knew exactly how she felt. As a doctor, he had qualms every time Sherlock handed over money for information, knowing that nine times out of ten, it would be spent on drugs.

"I'll take that up. He's in the bath; could be a while."

She smirked. "Sometimes I wonder what he gets up to in there. I mean the water must go cold after a while. Tell him he owes me twenty quid. I had to pay her for it." She handed over the paper, and then put her marigold back on.

John pulled out his wallet and produced a crisp twenty pound note which he tucked into her apron pocket. "I'll collect it from his wallet, before he gets out." John went back up the stairs, looking at what was drawn on the paper. It was a line drawing, incredibly detailed, of a building that John instantly recognised- St Pancras Station. A black felt-tip pen had captured every extravagant swirl and embellishment of the Victorian façade that graced the station hotel.

When three weeks later, Sherlock walked into the high-tech office of Abraham, Hartness & Holder, he was carrying the drawing. The architectural design company was one of the newest tenants in Four Pancras Square, in the heart of the regeneration zone that was turning one of north London's most run-down neighbourhoods into the most prestigious developments in the capital.

"I'd like to see Peter Fergus, please."

The receptionist at the glass reception desk eyed him appreciatively, before asking, "Do you have an appointment? I don't seem to recall Peter having anything in the office diary."

"It's a surprise. I'm an old friend."

She looked a little sceptical. "Your name?"

"But then it wouldn't be a surprise, would it?" He gave her one of his slightly goofy smiles but wouldn't make eye contact, "I'm only here for the afternoon- just got in on the Eurostar and have an hour to kill before a meeting."

"Well, I'm not supposed to let just anyone in unannounced. And I'm not aware that Peter has a lot of friends. He's sweet, but he kind of keeps himself to himself, if you know what I mean."

He could see her slightly protective reluctance, and decided to take a short cut. "Yeah- I know _just_ what you mean; it takes one to know one." Opening the folded paper, he put it on the counter. "Peter's handiwork; gave it to me when he first got to London. Now that he's made it big, I thought I would get him to sign it. Then I'll frame it and stick it on my wall to remind us of our geek days at the Central Design School. Go on, let me in, I won't take a minute up of his valuable time."

He wouldn't look at her, but kept his eyes down on the paper.

She caved in. "Oh, all right. Follow me." She led him down the corridor- on the right side was an open plan area overlooking the Regent's Canal. It was crammed full of architect design desks- all high tech computerised, plus a few old fashioned drafting tables that could accommodate the huge blueprints. The young professionals sitting at those desks looked very busy. AH&H was deeply involved in the regeneration work that would see more than twenty new office buildings and residential blocks going up in the immediate vicinity behind Kings Cross. The left hand side of the corridor was lined with private offices; the walls between the doors were hung with a series of framed renditions of the buildings that the firm had worked on. Sherlock smiled as he recognised the style- every one of them a black ink line drawing, instead of the more usual computer-generated image. Black line drawings were part of AH&H's new corporate identity.

She knocked on a closed door, and when there was a muffled, "Come in" from the other side, she opened it, but stayed on the threshold as if from habit, gesturing him in. Sherlock closed the door behind him as soon as he got in the room.

"Who are you?" It wasn't a friendly greeting. The brown haired young man was well dressed, with a sharp haircut style. His glance up had been very brief, before turning back to his architect's drawings, spread across a large glass table.

"Sherlock Holmes. I'm here as an emissary on behalf of someone." He walked over and dropped the St Pancras drawing onto the table.

That made Peter look up, and frown- but he still didn't make eye contact. "Emissary? From whom?"

"Your mother."

The man was shaking his head. "I don't have a mother. Not alive, anyway."

"Alex Barfoot has a mother, whose name is Abigail…."

The young man turned back to his blueprint, pushing aside the old drawing. "Never heard of her, or him."

"She's been divorced for two years, but still looks for her son everywhere- hospitals, homeless shelters, even the morgues."

Peter wrote a note on the blueprint. "Sounds sad. Nothing to do with me."

A silence fell. Sherlock used it to look around the office. It was tidy- no, more than that. Everything was…perfect. A rainbow of felt tip pens in a box that was just the right size to hold them exactly. The phone squared exactly with the edge of the clear desk. The bookshelf was arranged by size in descending order. Every leg of every piece of furniture was in its own dent in the carpet that said it had been there and always replaced exactly where it had always been.

Conversationally, Sherlock said, "Chlorpromazine, or Effexor?"

That made Peter stop writing. "How did you know? No one here knows." There was a tiny thread of anxiety now in his tone.

"Your mother said she was worried about you without your meds. One look at this office tells me you suffer from an anxiety disorder, probably OCD. That irritated your father, no doubt, but your mother must have managed to get you on something, over his objections."

Peter returned to writing. "I don't know what you are talking about. Please leave now."

"Not until I say what I came to say."

Peter put the pen down. "Then say it and get out." His anxiety was now tinged with anger.

"I told your mother that I would find you and then let you decide."

"Decide what?"

"Whatever you do or say now, I will tell her that you are alive and well. If you want, I can tell her that you want nothing to do with her ever again, and I won't tell her anything about your current name, where you work or what you are doing. That's one option. The other is that you tell me what you do want her to know, and I will pass it on- but again, protect your anonymity. Oh, there is a third option; I could give you her phone number and address, if you want to cut out the middle man and deal directly."

Peter was looking rather intently at the old drawing lying on the table in front of him. "Hypothetically speaking…if I knew what you were talking about, why would I want to do any of what you've just described?"

Sherlock moved further into the room, looking at the drawings on the walls, the smart furniture, before finally letting his eyes fall on the well-dressed young man. "Because she imagines you under a bridge somewhere, a drug addict sleeping in a cardboard box, hungry and ill. Or worse- on a slab in a morgue or an unmarked grave. And you are so obviously not that it seems wrong to let her keep thinking the worst."

Then Sherlock shrugged. "But, what do I know? You have your own reasons for leaving home, and I respect them. And you- for making a success of it. It's up to you, Alex."

"Alex is …dead. Peter is alive. I like Peter. He's successful. He isn't liked by many people; but people respect him. He doesn't need to remember a father who was beastly, and a mother who let him be so. Why would I want to change that?"

"She divorced him; maybe he was beastly to her, too, or she didn't like him being beastly to you. And she has spent the last four years trying to find you, just to know that you're alright."

"How did you find me?" He sounded both perplexed and worried.

"You left a drawing at the Shelter. You made postcards for tourists, in front of some of London's sights. I found one of those reproduced in a leaflet used by the London Walk guides. You sold enough to talk your way off the streets and into a flat-share. I got that far easily. Now for the tricky bit- Peter Fergus- your flatmate. He took me a while to figure out. A fortuitous collision- car versus telephone pole; he was the driver, you were probably the passenger and he died, you didn't. So, you took his identity- a well-off, single man with no family who had come to study at the St Martins Central School of Art and Design. He had liked your work enough to give you shelter- a man with a passport, driver's license and a wallet full of money. The passenger who died in the accident was just a homeless man with a made up name. You never looked back. I followed the decay trail, as you changed yourself into who you are now. A whole new person. Quite clever, actually."

"Is she paying you to find me? I'll offer you more to keep quiet."

Sherlock shook his head, knowing that Peter was now anxiously watching him, using his peripheral vision. "I'm not being paid, and this isn't blackmail."

"Then why would you search for me?"

"Because she is willing to give you the choice I was never given. I disappeared into London at about the same age as you. Only my brother found me, and put me into rehab. He never gave me the choice that she's giving you. Tell me what you want me to say to her."

The young man stood up, and really looked at Sherlock. "Have you forgiven him?"

Sherlock started to snap something sarcastic, but then stopped and took time to decide how to answer.

"It took me a decade to stop hating him for it. My situation was different from yours. You've made it without your mother's help. I'm not sure I would have without his. I'm not proud of that fact; maybe that's why I can't forgive him." He took a breath and returned to the subject, "So, tell me what you want me to do."

"Tell her that I'm alive. I don't hate her. Never did- just thought she was weak. Well, I'm stronger than that, so I left. You can tell her that I'm doing well." Then the young man looked away again. "Leave me her number. If I can think this through, I might get in touch. Or I might not. It will be my decision."

Sherlock reached into his pocket and drew out the photo of Alex Barfoot. "Her contact details are on the back. Good luck- whatever you decide." He started to go, but then stopped. "The drawing, will you sign it for me? I told the receptionist I was a fan, an old friend of yours from St Martins."

Peter turned back to the desk and used his black felt-tipped pen to sign the St Pancras drawing with a flourish. He handed it over the Sherlock, and said, "I don't have friends."

"Yes, you do. You just don't know it."

oOo

* * *

 **Author's Note** : This follows on directly from first two chapters of _Got My Eye on You._ But it stands alone, too.

* * *

Outside the police station at 6.45am, it was still dark. That was one benefit that Sherlock appreciated- fewer visual stimuli. He was having trouble with his senses- too long since his last hit, and his sky-high anxiety level was combining with withdrawal to make life difficult. The whole night had been impossible. Getting high, being caught at a crime scene, being brought in by a detective sergeant who realised he was underage and wouldn't let him go, even though he had no real reason to hold him- he could have coped with that. Once social services arrived at 9am, he'd spin his tales and manage to escape, as he had before.

But then his own personal nightmare in a three piece suit turned up. The full horror of that was manifesting itself in the vise-like grip on his left wrist, courtesy of a brother he had hoped he would never see again.

As soon as Mycroft dragged him from the station, the freezing air burned its way into Sherlock's lungs and made him cough.

"Serves you right for smoking."

The superior tone of his brother's voice rasped like sandpaper on Sherlock's senses. _Oh, shit. Not a good time for this to be happening._ He was going into sensory meltdown, just when he needed to be firing on all cylinders if he wanted to escape from the fat git. An experimental pull on his wrist was met with Mycroft's solid refusal to budge. His brother had put on weight since he'd last seen him, sixteen months ago, at their father's funeral.

Sherlock sniggered in slight hysteria. "I see that Washington's finest restaurants have enjoyed your patronage."

"What?" Mycroft resumed pulling him along, but looked at him intently as if thrown by what he thought was a non-sequitur. "Are you _still_ high? The police said you've been here for nearly eight hours."

Ignoring the question, Sherlock was trying to figure out what he was going to do to escape what he could see was coming. Ahead, by the kerb, the car was waiting, its exhaust adding a plume of smoke to the frosty air. The driver's door opened, and he vaguely recognised the chauffeur who got out- a young man who used to work at the estate's farm in West Sussex. Sherlock ground to a halt for a second time, and Mycroft stopped and turned to look at him, his frown apparent in the light cast by the street lamp.

"Let me go, Mycroft. I'm…begging you. You don't need to do this. Just leave me be." Sherlock's voice was shaky with emotion, the newly fledged baritone cracked into a higher pitched tenor.

His brother's eyes were cold. "Yes, I do have to do this, because you are being spectacularly stupid. Don't make this worse than it has to be."

"Worse? Worse than what? There is _nothing_ worse than what you are planning. Locking me up; how convenient for you."

Mycroft tightened his grip and leaned closer to him. "It won't be like that. You need help. Once you're off the drugs, then we can talk about what happens next."

He heard this as if from the bottom of a well. The crash and burn of withdrawal was giving him a headache that threatened to split his head in two. Every sense was hyperextended. Sherlock could smell his brother's smugness- the expensive aftershave, shampoo- even the shoe polish on the handmade brogues. He could see in minute detail the nick on Mycroft's chin that said he'd shaved too quickly. So much data was coming in visually that it was eating him up from the inside of his eyeballs. _My skin itches so much it actually hurts._ He could feel the in-out rasp of the cold air on his throat, burning into his lungs. The heavy weight in his chest, the coughing he should be doing to loosen the mucus- he just didn't have the strength to do it. And now these sanctimonious words and the prospect of being locked up for good.

It was just all too much; something inside him just snapped shut. He pulled Mycroft closer, as if wanting to say something, and then viciously drew his knee up hard into his brother's groin. There was a gasp, and a slackening of pressure around his wrist, which Sherlock used to his advantage, tearing his hand out of Mycroft's grasp. In a split second, he'd spun away and started to run as fast as he could away from the car.

He made it around a street corner and almost fifty meters before he was caught in a flying tackle by the chauffeur. Later, much later, when he had all the time in the world to think about it, he realised that running when he'd not had anything to eat for more than a day and was suffering from his third week of pneumonia wasn't the brightest idea he'd ever had. At the time, all he could manage was surprise as he felt the weight of the farmer's son land on him before the pavement came up to smack the side of his face.

When consciousness returned, for a moment he had no idea what had happened or where he was. That in itself wasn't unusual. Sometimes he lost track of time and place when under the influence of drugs. He'd learned how to assess his situation before opening his eyes and letting anyone in the vicinity know that he was awake.

Within seconds, he realised that this was different on so many levels. Sounds came filtering through something…muffled. His hearing was being interfered with by something wrapped tight around his head and ears. Then all thoughts about that went away as a shroud of pain descended. His face and head hurt. But that too was muffled by something- it was pain, but not as he usually understood it. The ache was as if felt at arms' length- he knew it was there, and that it was serious, but somehow it was being kept distant. He instantly recognised the effects of opiate drugs. He'd used enough heroin and morphine to know its effects.

The fact that he had no memory of using it wasn't in itself unusual. Since being on the streets, he often lost track of things. Black holes of memory were something he'd learned to negotiate around, like unexpected pieces of furniture being moved into his bedroom in the night. Despite the darkness, feeling around carefully was better than walking straight into them.

So he waited a while longer, listening and feeling his senses slowly come back on line. One of the muffled sounds was a beeping that he didn't recognise: rhythmic and mechanical. Then his nose woke up and he remembered the scents, realising instantly that he was in a hospital. Oddly, he heard the beeping suddenly increase its pace.

"Hello, Sherlock. It's alright. You're safe."

Calm, quiet words, designed to reassure, spoken in a woman's voice, one he recognised. _Doctor Cohen._ He tried to speak but a weird noise emerged, more a grunt and gasp than anything coherent to match his instant panic. His worst nightmare was coming true. He kept his eyes closed, but tested his hypothesis by pulling at his right hand. It moved a bit, then stopped, held fast by a cuff restraint around his wrist, no doubt secured to the metal bar on the side of the hospital bed. He could feel bandages on his hand, too- a crease of pain shot across the palm. The next sound he heard was his own voice, in a panicked "Nooooo!"

"Please don't. Don't fight, don't struggle. You will just hurt yourself again and then we will have to sedate you. You desperately need to clear the drugs we've already given you before things will make sense, so don't force us to add more. Keep your eyes closed to limit the sensory stimuli. Try, this time _really_ try to stay calm."

 _This time?_ What was that supposed to mean? He was momentarily stalled in confusion, trying to remember what had happened to end with him tied to a bed in a hospital, trapped in his own personal vision of hell. He managed to get his tongue unglued from the roof of his mouth to mumble out, "what happened?"

"To answer that, I need to know the last thing that you can remember."

Sherlock tried to think, which was difficult through the gauze of the opiate. Then it came back to him, standing on the pavement, the look of surprise and pain on his brother's face as Sherlock's knee connected with soft unprotected flesh under the Italian leather belt. He hissed, "Mycroft…got what he deserved, the prick."

"Oh." Doctor Cohen sounded surprised for a moment. "Then listen carefully, because a lot has happened since. And it is the reason why you are in here, restrained. Before you start blaming your brother, you need some facts."

He moaned. He didn't need facts. His brother was factual enough. Solid, immovable. The disapproval on his face, in his posture, had said everything Sherlock needed to know. He had to figure a way to escape.

"You hit your head when the driver caught up with you, outside the police station. That was four days ago."

"Four days?!" That blurted out without him thinking, in a high pitched shriek. _I've been locked up for four days._ The beeping was now beating out a frantic staccato rhythm, as if betraying his panic. He realised it was a heart monitor. It was an invasion of his privacy, a noise that undid any attempt of his to hide his body's stupid weaknesses.

"Should I get another dose of Lorazepam, doctor?" It was a quiet voice off to the right, one he didn't recognise, a man's voice. _Nurse?_

"Not yet…Sherlock. Please, just listen. You were knocked unconscious and needed an ambulance. Mycroft was scared you'd fractured your skull. On the way to the hospital, you woke up in the ambulance and went into meltdown. The crew had to call in and get permission to sedate you, because they thought you'd hurt yourself even more. At the hospital, they did an x-ray, then a scan, because they were worried that your brain was bleeding or swelling. You woke up in the MRI machine and panicked, thrashed about so much they had to sedate you again. Do you remember any of that?"

He tried to remember, but could only recall noises- a loud wailing siren and banging, loud metal thumps that made him think he was in a coffin and his brother was on the outside trying to smash his way in. _I'm already dead; leave me alone._ He tried to get his breathing under control. It hurt- his throat, his lungs. He coughed, and it sounded wet, even to his ears.

"Yes. You have pneumonia. But you knew that, because you were taking antibiotics. You got them from a walk-in clinic three weeks ago, according to the bottle. They were prescribed to an L. Sigurson- which matches the ID that you gave the police. Actually, the pneumonia has improved over the past four days- probably because of the IV antibiotics, and we've been feeding you through a gastric tube- that's why your throat feels even more sore. You've been getting extra oxygen, too. Do you remember what happened when you woke up from the sedative the next time?"

He tried, but came up blank. He started to shake his head, but stopped, because it hurt too much to move.

She sighed. "The concussion was pretty nasty, and some memory loss is normal. So don't worry. But, what happened when you woke up is the reason why you are here, and your wrists are restrained. You were in an adolescent ward at UCH; you woke up in the middle of the night. The ward sister wasn't in the room when you took out the IV and got out of bed. You went down the hall, picked up a chair, smashed the window and started to go through it to get out. Trouble was, you were in such a state that you didn't realise that you were on the seventh floor. If the nurse hadn't stopped you, you would have fallen to your death. Your hands were cut by the glass, and you were screaming your head off about Mycroft stealing your body. It was…a pretty wild psychotic episode. They used a heavy duty dose of Haloperidol and you've been out ever since. You were moved here, to stop you from hurting yourself- or worse."

He mumbled, "where's 'here'?"

"The Priory, North London. You really don't remember any of that happening?"

"No." He wondered if his reply it sounded as sullen to her as it did to him. He hoped so. She needed to know just how annoyed he was by this turn of events. In case she'd missed it, he added, "there I was minding my own business, not hurting anyone, and then suddenly because my brother's an interfering megalomaniac, I'm tied to a bed, in pain. Why do I need to remember anything more? "

"He's been looking for you for six months, Sherlock."

" _WHY?!_ I didn't ask him to. I wasn't _lost_. I got rid of him, escaped, disappeared, not to be found, happy to be that way. I _like_ being on my own, undiscoverable –just why couldn't he leave me alone?" This came out too close to a wail for his liking, but at least she would know what he was feeling. "I was fine until I collided with him. Now, everything is split up, confused, fractured. This is _his_ fault."

She shifted in what he guessed was a chair by the bed, given where her voice was coming from. "Nurse, please turn off the lights, and leave us."

"You sure?" The man didn't sound convinced. Somewhere, through the fog enveloping him, Sherlock thought that was funny. He was tied up, spread-eagled like some lab specimen, in so much pain that he didn't dare move, and so drugged that he didn't think he could move even if he had wanted to. Yet, the male nurse sounded like he was reluctant to leave the psychiatrist alone with him- as if he might try to hurt her. _Hey, what about ME? I'm the one who needs protection from all this!_ If Mycroft had only left him alone, he'd have been okay.

Whatever she did, it was enough to convince the man to leave. There was a sound of the switch, and then the infernal buzzing of a fluorescent tube stopped.

"Okay; it's safe to open your eyes now."

He did, slowly. His left eye didn't seem to want to open. Instinctively, he reached his hand up, only to hiss with pain when the cuff bit in and made the cut across his palm flex again.

"Your left eye is swollen, Sherlock; you may not be able to open it. The doctor says it's just badly bruised, so not to worry about it."

His right eye was now open and focused on Esther Cohen. She hadn't changed much in the two years since he'd last seen her. The look on her face was composed, careful, watchful.

"Sherlock, you need help. I know that what happened with McGarry was horrible, and running away was…understandable, in the circumstances. But you've got family and friends who care about you and have been trying to find you for months."

"I don't have friends and I hate the only member of my family that's left." He was disappointed that he could hear the wobble in his voice, and distressed that he couldn't stop his one good eye from tearing up. He felt an odd sensation, as if something had gripped the centre of his chest from the inside. It was something he had not felt for a long time, but it was rapidly followed by a sharp pain around the cuticles of his fingernails. He never understood that- why his fingers hurt when he was seized with utter despair.

"Yes, you do have friends, you just don't realise it. And your brother certainly doesn't hate you. He's moved heaven and earth the past six months to find you."

"Don't believe him. He's _lying. Anyone_ who says they are a friend of mine is lying; they work for Mycroft and their job is to keep me under his control. Make him let me go. I want out. Please, anything but hospital." Now his right eye was definitely crying; he couldn't see through his left eye to know what it was doing- it hurt too much.

"I know that this has unpleasant memories for you. That's understandable. But you aren't ten years old this time. This isn't like what happened then. You're old enough and smart enough now to know that this is…necessary. For a while, until we can…"

He interrupted her, his distress pushed aside in a blaze of anger as he tried to sit up. " _WE?!_ Who's _we_? There's no me involved…I don't want any part of this. You and Mycroft are conspiring to lock me away forever, so don't expect…" Whatever else he might have added got swallowed up in a burst of coughing which made him feel like his lungs were on fire. That made his head nearly burst with the pain, and he collapsed back on the bed. Blackness took him.


	3. Chapter 3

**Summary for the Chapter:**

> Berkelium was first produced in December 1949, when scientists at University of California at Berkeley took americium-241, made by bombarding plutonium with neutrons, and bombarded it with helium nuclei (alpha particles) for several hours in the 60-inch cyclotron. They dissolved the target in acid and used ion exchange to separate the new elements that had been created. This was the isotope berkelium-243 which has a half-life of about 5 hours. It took a further nine years before enough berkelium had been made to see with the naked eye, and even this was only a few micrograms. Sometimes, it takes a very careful observer to see what everyone else has missed.

 

It was late autumn, and John hunched his shoulders, and pushed his gloved hands a little deeper into his pockets to escape the stiff wind that was blowing up Baker Street. He'd been out on an errand- dropping off some dry cleaning. A nasty blood stain on a favourite shirt; he'd got it when they were trying to interview the daughter of a victim and the murderer showed up to try and add her to the body count. The blood wasn't his; it was the murderer's. Sherlock and Lestrade had tackled the guy before he could do the deed, and he got cut by his own knife. John did the first aid on the knife wound while a constable was cuffing him- but managed to get his right sleeve in the guy's blood. Fortunately, Sherlock recommended a cleaner who specialised in removing blood stains and "unknown bodily fluids. No questions asked, which makes the service even more valuable. Just put it on my tab." The dry cleaner reassured him. "To the naked eye, sir, the stain will be invisible." John had thought it amusing that Sherlock would have a standing account there- but then in his line of work, stains must be an occupational hazard.

He was just reaching his key up to the lock when the door was thrown open and a tall consulting detective came charging through, nearly knocking him over.

"Oh, John. Good. You're back. Come on, Lestrade says there's something interesting at Kings Cross." This was said over Sherlock's shoulder as he strode to the kerb side and thrust his hand up in the air to attract the attention of a cab that just happened to be coming up the street.

John wasn't sure whether he should be more startled (he was), or more annoyed by Sherlock's automatic assumption that he would go with him (he was). But he wasn't surprised that within a few seconds he was standing alongside Sherlock as the cab pulled up. This was life with Sherlock, and whatever else it was, it wasn't boring or predictable.

In the back of the taxi, he turned to Sherlock who was already working on his phone, tracking something down. "So, what's it this time?"

"Dead body, found on the tracks of the Eurostar station at St Pancras. According to Lestrade, 'it doesn't make sense.'" Sherlock smirked. "You'd think after twenty years as a detective, he'd be better at making sense of a dead body."

"What, and do you out of a job? You'd _hate_ that- no chance to show off what a clever clogs you are." It was said with affection.

The Euston Road was quick and it didn't take them long before pulling up at the Eurostar station entrance, off Pancras Road. Sherlock texted just before they arrived, so when they crossed the concourse, Sergeant Donovan was there alongside a Transport Police constable in a high visibility jacket. The departures and arrivals board above his head bore mute testimony to the incident- every single train listed coming in or going out was marked by the word "delayed"

Donovan looked impatient, and just said to the TP Constable- "Holmes and Watson. Now can I get back to work, please?"

The constable gave them an apologetic smile. "Sorry, SOP requires visual identification, Sergeant Donovan." She rolled her eyes.

The TPC shrugged, and said, "I'll lead the way then. It's a little complicated if you're not familiar with the layout of the station." He led them through a jam-packed departure lounge, full of disgruntled passengers, up to the locked double doors for Platform five, swiped a card and then took them up the escalator to the Eurostar train. John had never taken the sleek white train, and was surprised.

"Wow- that's _long_!"

"About 400 meters," said the constable.

"394, to be precise," corrected Sherlock. "The maximum allowed length of the British high speed trains is 312 meters."

Donovan just muttered under her breath. "Bloody train spotter- how could I not have guessed that?"

John had some sympathy. Sherlock could happily delete the finer points of the solar system, but still be able to quote you the precise length of a train. "Why do you know that fact?"

"Murders happen on trains. Bodies on tracks- don't you remember the defence plan thief?"

John frowned. "His _name_ was Andrew West, Sherlock. How can you remember the length of a train but forget the name of one of the victims in that crime?"

"You were in the lead, if I recall, John. Anyway- he was just one victim. Details about trains, on the other hand, solve a _lot_ of cases. It pays to know how the rail systems work in London because they are conduits of crime."

John stored that little bit of Sherlockian perspective in the file marked 'sociopathic tendencies'. Or was it just a reflection of his ruthless logic? No room in the hard drive to waste on a single victim's name, when it might be crucial to a future case to know that Eurostar trains were longer than any British train?

Walking to the end of the platform took them right out of the original station, with its single span of glass roof, on through a new extension, and then into the cold open air. At the end of the train, the platform stopped only a few meters on, and then John could see the tracks- there must have been at least ten, with signals crossing from line to line to allow trains to move across and out to the north. To his far right was another pair of platforms that jutted out even further- the nearest of the two had a train on it. It didn't have the familiar blue white and gold livery of the Eurostar train on their platform. This train was dark blue with gold livery.

As they came to the end of the concrete, there was a single strand of police tape across it. Sally lifted it and jumped down, ignoring the three men as she strode off quickly. The Transport officer told them, "You don't have to mind this set of tracks- no overhead electric; it's diesel this side of the channel." They headed to the group of people standing in a knot about eight hundred meters from the end of the platform. More TPCs and Met CSEs were walking the tracks, looking carefully for evidence, moving slowly in a straight line towards the station.

Lestrade looked up and nodded as the pair arrived. He was talking to a middle-aged tall man in a high vis jacket over his smart woollen coat. Just by the body language, John guessed that this would have to be someone senior. And he was looking decidedly unhappy and harassed.

The DI introduced them. "This is Sherlock Holmes and Doctor Watson; the consultants I told you about. This is Mark Gerrard. He's Station Master here. He was in the control room when the body was reported." John took in the man's glasses, the salt-and-pepper dark hair now showing grey. He was wearing a suit under the coat and jacket, and an ID badge hung on a Network Rail lanyard.

"Finally! Every minute we waste here is literally costing thousands of pounds and pissing off thousands of travellers, so I'd appreciate it if you could do whatever you have to do as quickly as possible." His look of irritation was mirrored on the faces of the other two Network Rail staff

Ignoring everyone, Sherlock moved past the man and knelt beside the body. John gave the Station Master an apologetic smile, but hurried after so he, too, could focus on the body that had brought them to the crime scene. He pulled off his leather gloves and put on his latex gloves as he crouched down alongside the consulting detective.

Sherlock was looking, really looking; his eyes were scanning up and down the body. It was badly damaged; bloody and broken bones were evident – John spotted compound fractures in one leg and an arm. The original blue and white Eurostar uniform was now a kaleidoscope of colours- dirt, grease and blood. The man was missing one shoe, his bare foot turned at an impossible angle. The other foot was a mangled bloody mass of shoe leather, sock fabric, blood and bone. However it happened and whoever had done it, the death had been horrible.

John put his hand on the side of the man's neck- stone cold. "This isn't recent; even in this temperature, it's been a couple of hours. Multiple fractures, internal bleeding." John lifted the bloody head, feeling the neck bones. "Cause of death is likely to be a broken neck, or the massive skull fracture." He could actually feel the skull bones grating, where the brain case had been split.

Sherlock was still focused on the body, pulling out his pocket magnifier and lifted the man's right hand. The left had been ….well, the best word John could use to describe it was 'mashed' to a pulp, with the bones hardly recognisable.

"Tell me who spotted the body and when." Sherlock's peremptory order was aimed in the general direction of Lestrade, but it was the station master who responded first.

"The driver of the 10.18 Eurostar arrival from Paris called it in. He was stopped up there." Gerrard pointed further up the track, "that's the last holding signal before station entry. The driver said he could see something across the track- wasn't sure what it was, so called the box. He's still there, dealing with eighteen carriages of pissed off travellers and French business men who want to know why for the last forty minutes they can't get to the station that they can see right in front of them."

"What was the last train to cross this signal?" Sherlock stood up, looking down at the track on which the body was sprawled and then back down the line to where John could see the criss-crossing tracks that were needed to join up the many platform tracks to the actual rail lines heading north. It was hard to see what led to what from this angle, so low on the ground.

Gerrard had come up to them now. "The 10.03 departure from platform six went across this point. That's what's so strange. The driver didn't report anything amiss. We've spoken with him on the radio since to confirm; he's past Ashford International now." Gerrard took a very quick look at the body. "Given the …uh… damage, it looks like this guy must have jumped under the train?" His statement had that interrogatory uplift at the end of the sentence; the one that made it sound like a question. "Maybe he fell from the platform and his body got dragged this far? The TGV design is quite low to the track."

Lestrade butted in. "We've not found any ID. The uniform is for Eurostar catering staff. But no one has been reported as missing yet. They're still trying to track down some of them."

Sherlock stood up, but kept his eyes focused on the tracks in the distance. "Did the outbound train leave on time?"

The Station Master's brow furrowed. "Yes and no, depends on what you mean by 'on time'." John was confused by that, but Sherlock just nodded.

It was Lestrade who asked the obvious question. "You'll have to explain that, Mister Gerrard. It's either on time or late, how can it be both?"

The man tugged the front of the high vis jacket smooth, as if he was unused to wearing one. "According to Eurostar's service commitment, the train is not late if it leaves within seven minutes of its designated departure time. We keep very accurate records, because if it is the station's fault, then we get fined. If it's the train's fault, then they carry the cost, should a passenger complain. It leads to a lot of complicated paperwork. And right now, every second I waste dealing with questions like these just add to the pain of paperwork and pounds off our income."

Sherlock was ignoring the conversation, instead turning from the body to look back into the station and its platforms. His brow was creased in concentration, but John could tell from his body language that something was up. "John, in your opinion, are the injuries consistent with being hit by a train?"

The doctor thought about it. "A coroner will be able to tell more definitively. There are crush injuries, but…"

"Exactly, _but_ …. _but_ the speed with which these trains are going in and out is controlled to under ten kilometres an hour. _But_ the injuries are more from a crush than an impact. _But_ , the position of the body is all wrong for someone hit by an incoming train. _But,_ the outbound train would have run over the various body parts that are across the tracks, severing them. There are too many _buts_. And just where is the shoe, not to mention the sock?" He turned to the DI. "Get your people to find those; then we might get somewhere."

Lestrade looked at Sally, who gave a disgruntled sigh and said, "They're already walking the scene looking for trace." Greg just prolonged the look until she caved in. "Alright." It was a long-suffering reaction. She pulled up the airwave radio and started speaking into it, as she strode off to the line of officers.

Sherlock was still shaking his head. "I need more height. I need to _see_ the whole picture."

Gerrard snapped, "Whatever helps get the trains moving again. There's a better view from the control room. I'll take you there."

It was a circuitous route, but a few minutes later, John was standing beside Sherlock, looking out of the control room's plate glass window, and seeing now for the first time just how complicated the track lines were. Behind him the control room was quiet. The workers were standing about, made idle by the enforced shut down of all services. Gerrard had been greeted by a barrage of questions which he batted away with as much commiseration as he could get away with.

He came to the three of them standing at the window. "We've got twelve more minutes before the delay destroys the day's profitability. If we have to delay all of the trains for more than an hour, we end up in deep trouble. Performance targets and all that." He shrugged his shoulders. "And we really try not to inconvenience the passengers. The needs of the thousands of commuters and tourists, not to mention the train companies who serve them, mean that you'd best get this sorted as quickly as possible. PUTs are just a pain in the ass."

"Puts?" John didn't understand.

Sherlock answered before Gerrard could. "Person. Under. Train. P.U.T.s. However, I can assure you that unlike the majority of PUTs, this one is not a suicide."

"That's what the Detective Inspector said. So, what value are you adding to this discussion?" He did nothing to hold back his irritation.

"Fewer complaints and more facts, Station Master. Tell me what we are seeing here."

Gerrard glared, but then, through gritted teeth, explained. "Okay, start with what you can't see from up here- Platforms A and B , the First Capital Connect Trains. They're underground at this point, don't come over ground for another kilometre. Their platforms are on the lower level. The FCC network links up Wimbledon to the west with Beford and Luton to the North. Then there's the Bedford Brighton line and the Kent service goes to Seven Oaks."

Gerrard pointed out the window to the left. "Platforms one to four out there are East Midland trains, accessed from the Arcade on the Lower Level. The tracks are separate, and don't connect operationally, just for access to the maintenance spur to the north. Three quarters of a mile out those tracks merge with the Midland Main Line. Then to the east, platforms eleven, twelve and thirteen are the javelin trains; some of them use the the ThamesLink line, others use HS1, so the signals conjoin the services. All of the Javelins are accessed by ticket controlled barriers from the Circle on the lower level. The seven tracks in between are Eurostar's platforms. They are controlled by electronic doors from the secure departure lounge, up escalators. It has to be secure because of passport controls; Britain's not in the Schengen agreement, so we have to keep tight watch of who gets on and off those middle platforms. There's no CCTV footage of this guy on any platform, by the way."

Sherlock was consulting something on his phone. "Putting all that together, how many trains in and out in the space of an hour, from nine am this morning?"

Gerrard pursed his lips. "Just under thirty, I'd say off the top of my head. We think of them as discrete services, but I can get you the specifics if you need them." When the DI nodded, he turned to one of the workers behind him and asked for a consolidated timetable.

John was staring out over the tracks, his gaze fixed on the knot of CSEs working the taped off crime scene around the body. He could see that another person suited in the blue forensic kit had arrived; probably the medical examiner.

Lestrade asked the next question and it made John turn away from the window. "What about access from the other direction- you know, on foot, over a fence and onto the tracks from the side?"

Gerrard shook his head. "Unlikely. The station approach is high security fencing all the way in from Stratford. There was so much fuss about the stowaways on the Euortunnel Shuttle trains coming from France that when the HS1 line was built, they made sure it would be very hard. The Border Agency routinely check. So, it's not like someone could…I don't know, _wander_ onto the tracks- not unless he walked from Stratford International. Anyway, the uniform says he's staff."

Sherlock huffed. "Or, that is precisely what we were meant to think. There is catering on these trains so it has to be delivered- and that involves ramps and trolleys that are not coming onto the platforms the way passengers do. I want all the freight access routes, too."

The station master nodded and turned to one of the control room staff. "Pull out the floor plate plans."

A few minutes later and the four men were leaning over a glass table, looking at large blueprints, whose curled up edges were being held down with paperweights. There were six different sheets, one for each level of the station. After ten minutes of scrutiny, Lestrade sent his PCs off to investigate six routes that a train crew or station worker might have used to get onto the platforms and tracks. CCTV cameras in the freight and mail areas would also be recovered so they cnould be trawled later.

In the meantime, the body had been removed. John saw the body bag being lifted onto the stretcher. Gerrard saw it too. "Can we resume services now, _please?!"_

Lestrade checked with Donovan that the walk-through up the line was complete and that no trace evidence remained to be bagged. "Sherlock? Is it ok to open all of the lines except Platform Five?"

"No shoe? Or sock?"

The DI spoke into the airwave, then shook his head. Sherlock narrowed his eyes, and turned back to the window again. Gerrard was getting increasingly impatient.

John was watching Sherlock, who had walked away from the window and was now standing to the side of one of the computer workstations. He had that far-away look; eyes open but not focused on anything in particular.

"Sherlock?" John said this quietly, then touched him at the elbow to try to get an answer.

"Hmm?"

"Can they start the trains again?"

Sherlock nodded, distracted by something else. Behind the pair, the doctor heard a peeved Station Master heave a sigh of relief, and then shout "Alright! Let's get this station back online!" Suddenly there was a frenzy of activity as the idle workers dashed for their chairs, picked up phones and the noise levels suddenly escalated dramatically.

Lestrade walked over to the two. "Anything? Come on, Sherlock. We've been here for a half hour; surely you've got some ideas by now?"

"Ideas? Yes, of course. Lots of ideas, Lestrade. The problem though is making sense of them. Let's start with the fact that this was _not_ a Eurostar caterer. No one in the food business would hire a man whose personal hygiene was so poor."

John tried to square this observation with the bloody and broken mass that had been a body. Lestrade looked equally sceptical. Sherlock picked up on their reaction and frowned. "Oh, you two- for once, just look beyond the obvious. The man had appalling BO; and his exposed skin was almost black with ground-in grime."

Greg's frown dissolved into a look of disbelief. "You could actually _smell_ sweat through that carnage? Geez, John's blog was right; you _are_ half blood hound."

Sherlock just snorted. "The body was placed, rather than killed there. When Sally gets through terrorising the Transport Police, she'll still come up empty- no trace of blood elsewhere on the tracks. He wasn't run over by a train- or, if he was, it certainly wasn't here. The missing shoe tells you that. And the idea of him throwing himself under a train is just ridiculous. No one about to commit suicide takes one shoe and one sock off, do they? That would be just…bizarre."

John followed his line of thought- to a point. "But how did someone just…put the body onto the track without being seen?" He pointed out the window. "I mean, wouldn't it be obvious? The gap between the one train leaving and the other one coming was more than ten minutes. There are passengers, train staff, the station workers. How could someone just blithely carry a body through all that and then walk up the track half a mile without being seen?"

"That's not the most important question, John. What you should ask is w _hy_ would someone go to such lengths?" There was a little puff of frustration. "As for getting the body there, it's all about angles and trajectories."

Greg and John looked at each other; neither understood what Sherlock was on about. By now, Gerrard had returned to them, having set his staff in motion. There were questions in his eyes now, as he looked at Sherlock. "What are you talking about? Angles, what angles?"

"Shut up."

Gerrard was startled by Sherlock's rude reaction and started to react, but John put out a hand to try to forestall that.

Sherlock ignored them. Drawing his hands through his hair, he looked blankly out the window, muttering. "The complexity of the layout is…annoying. Too many variables. Can't visualise the routes, the points, the speeds, the blueprints…" He ground to a halt.

"What is it?" John could see that some connection had been made.

Sherlock looked back at the table, and then he suddenly he was in frantic motion, swirling around the table, moving his head up and down, changing the angle of his look at the blueprint. Then he stopped, and a hand went out to trace in the air the way the station's plans were aligned with the edge of the glass table. "Reminds me …something… elusive, a memory, just barely there. Something I've seen before– a while ago, just a glance."

He turned to the wall and brought up his hands, steepling them in front of his mouth, touching the fingers of one hand against another in seemingly random taps.

Gerrard turned to Lestrade and John with a startled look at the consulting detective's increasingly odd behaviour. "Uh, has he gone off his trolley?"

John gave a reassuring smile. "Don't worry- he's _thinking_. Something he's seen here is important but he's not sure; it's not coming to the surface, so he's gone hunting for it. He sort of 'checks out' when he does that."

_He was wandering rather aimlessly down a corridor of his Mind Palace. He stopped briefly at a door that looked promising. Opening it, he walked into the Gilbert Scott bar of the Renaissance Hotel. Irene was sat at the bar, and she turned to smile at him, raising her glass of champagne in a toast._

No. Not you. Not now _. He backed out of the room in a hurry and turned to the left. This corridor was more recent. Then he noticed a frame on the wall between the doors- a black line drawing of the hotel's façade. This is more promising! He opened the door and walked into Peter Fergus's office at AH &H. The brown haired man was seated and didn't look up, bent over his glass topped table with the blueprint spread just so perfectly aligned with the edge of the table. Sherlock went over and looked over his shoulder as he made a small note on the paper._

" _OH!"_

Gerrard visibly started at Sherlock's exclamation and looked up.

Sherlock's smile was almost triumphant. "Lestrade, I'm not the best one able to answer this question, but I know _just_ the man who is. Come on. There is someone we need to talk to." He scooped up the blueprints from the table and in a swirl of coat, Sherlock bolted from the room, with John and Greg close on his heels.

Fifteen minutes later, the trio were standing around another glass table. This one was in a meeting room of Four Pancras Square, in the offices of Abrahams Hartness & Holder. Lestrade had flashed his badge and got them in, while Sherlock disappeared up the corridor to find the person who he said would be able to help.

A reluctant Peter Fergus was now bent over one of the blue prints, deep in conversation with Sherlock. The young man's soft voice scarcely carried to where the detective and John were standing. When the young man had first come into the room, the doctor was surprised to see a momentary look of panic skitter across the serious dark eyes, but Sherlock stood firm behind him in the doorway, as if to block his escape.

"I really don't think I can help you." The young man turned back towards Sherlock, with more than a hint of anxiety in his tone of voice.

Sherlock answered quietly, "yes, you can, and you will. It won't take long. But, your eyes will see things mine can't. You're better at reading these than I am. There is something I'm missing, but you won't."

Fergus then just grabbed the blueprints from Sherlock, spread them out on the board room table, and then ignored the doctor and the DI completely. John and Greg exchanged glances, wondering who the young man was and why they were here. That's when John caught sight of the framed print on the wall above the board room table- a line drawing of an old building, meticulously drawn in black ink. He walked over to look at it more closely. According to the small label beside the frame it was an old grain store, now refurbished as the home of the St Martins School of Art & Design. He recognised what it reminded him of, and drew in a sharp breath, which caused Sherlock to look up at him and then shake his head firmly. A moment later, the consulting detective was standing in front of the doctor.

"Don't. Not a word." This was said in a whisper.

"But, Sherlock."

"No, John. You are wrong. A case of mistaken identity. And not one that in any way should be discussed in front of a police officer." His baritone was firm.

"What are you two on about?" From across the room, Greg looked wary.

"Nothing that concerns you, Lestrade. Now, if you don't mind, I need to go back to work."

A moment later the young man stood up, straightening his back and nodding. "I've found it. There's an anomaly on the sub level three." He showed something on the blue print to Sherlock, who traced his finger along the paper. He went still for a moment, his eyes closed, while John and Lestrade came over to the table and looked over Fergus's shoulder.

" _Oh!"_ This time it was whispered. Then Sherlock opened his eyes, and gave Fergus a big smile. "Yes, of course; now I see it. Thank you, Peter. That was…most enlightening." He scooped up the blueprints and bolted towards the door. "Come on, John. The pieces have just fallen into place"

Greg and John hurried past the brown haired young man.

"Mister Holmes." It was said loud enough to carry down the corridor to Sherlock, who ground to a halt briefly, and looked back.

"My mother… she says… " He stopped, then shrugged. "Thank you."

That raised a smile, this time a genuine one, with the quick reply: "Good, that's good." And then Sherlock turned and strode out of the office toward the stairs.

As the three men walked back down Kings Boulevard towards the station, Sherlock filled them in. "It's a smuggling operation. The goods are brought in on the Eurostar trains in catering supplies which are unloaded and taken down to the sub-level by forklift truck. According to Fergus, we should look for a false wall, built onto the side of the store room. It will look real because it's been there since the start- the space is no more than a meter and a half wide, by about twenty meters long. My guess is cigarettes- easy to transport, lightweight and without tax, much, much cheaper on the continent than they are here."

As the trio cut across Battle Bridge Place, Lestrade said, "Sherlock, slow down, What's the connection between the dead body and this smuggling scam?"

The consulting detective eyed the steady stream of traffic coming up to the turning circle in front of the East Midlands line entrance. Judging the speed with split-second timing, he crossed between a black cab and a silver BMW. John was used to his unorthodox pedestrian habits and kept pace, narrowly being missed by a driver who leaned on his horn. More cautious, Lestrade was left stranded behind.

On the pavement outside the Eurostar entrance, Sherlock turned and looked surprised to see Lestrade coming up the walkway at a run.

"What happened to you? Decide to take the scenic route?"

"Just shut it. No- don't- tell me what the hell is going on here."

"You need to investigate the catering service. See how far up this goes. It's obviously a well-established operation, given they managed to get their store room built into the specifications of the new station. The fact that the body was put into a catering staff uniform is the key- it was designed as a warning. Probably a rival cigarette smuggling operation trying to smoke out the opposition."

As they went back into the station, Lestrade grabbed Sherlock's arm. "Just hold on, Sherlock. Where are you going?"

"Down- sub-level three, where I suspect we will be able to find blood, a missing shoe and the contraband goods, and put the smugglers out of business. They didn't do the murder; but by putting them behind bars, we will be doing what the real murderers want us to do- eliminate the competition. But at least one group will be behind bars."

Now it was John's turn. "Who is the dead man on the tracks? And how did he get there?"

"He's…nobody. Down on sublevel three we will also find a forklift truck that was used to crush a homeless person. Probably lured down there by the promise of free cigarettes. The nicotine stains on his right hand fingers suggest he was used to rolling his own. The homeless man was someone that no one would miss. Killed by somebody who dressed him in the catering uniform and then put him on the tracks, where we would find him. He's a victim alright- a pawn used in a turf war."

"So, how did he get onto the tracks with no one seeing him?"

As they went down the escalator, Sherlock stopped and looked up at the two men. "Because at one precise moment between 10.03 and 10.07, the East Midlands train from Bedford that was coming into platform 4 and the 10.03 bound for Brussels going out from Platform five came within a meter of each other- and no one would be able to see what happened when the body was pushed out of the Midlands train by the rival gang."

An hour later, John was sitting at a table in the Caravan restaurant, in the basement of the St Martin's Central College of Art & Design. As he tucked into his pizza, he asked Sherlock "How the hell did you figure it out?"

Sherlock was picking around the edges of a smoked mackerel fillet. "The lifestyle of a homeless person leaves visible traces, John. His feet, hands, the length of his hair. He had not had a wash in weeks. And unfortunately, the homeless are not usually missed when they die. After all, unless their fingerprints or DNA are in the system, it's almost impossible to identify a person who wishes to remain invisible."

He took a bite, chewed thoughtfully and swallowed before resuming. "Once I realised who he was, then it became simply a question of figuring out who would benefit from us finding him there. The challenge was being able to visualise how the smuggled goods got on and off the train, and where the evidence would lead us."

"And if you hadn't been clever enough to find the secret storeroom?"

"Actually, my guess is that is what the murderers wanted- someone to snoop around, but not actually put them out of business. Probably designed as a warning shot, maybe as a way of extorting protection, hush money."

"And a poor homeless person paid the ultimate price." John licked the tomato sauce off his finger. "Speaking of homeless people, was that guy Alex Barfoot?"

Sherlock looked at him sternly. "No. Alex Barfoot is dead. You met someone named Peter Fergus, an up and coming designer working in a very successful architect's firm."

"Who just happens to have been re-united by you with a long lost mother?"

"I facilitated… a possibility. Aligned a pair of atoms so they could collide. That's all; It was his choice whether it happened or not. It could have taken years, or it might not have ever happened at all." He shrugged and went back to eating his lunch.

oOo

He was half way through the sixth energy level notations on the electron configuration tables of the actinoids when he realised that he really needed to start writing things down. They had finally allowed him paper- but refused to supply a pencil- so he was reduced to using crayons, like some child. He was working his way through the elements 89 to 103, an interesting group. He had reached Berkelium. He scrawled

_Bk 6s2 6p6_

"Sherlock, why are you writing these symbols? What does it mean?" Doctor VIkram Walid was standing behind Sherlock who was writing at the desk.

He couldn't, wouldn't tell him. He hadn't spoken since arriving; he was hardly going to start now. The consulting psychiatrist at the Priory's Adolescent unit was one of "them". "They" were a collection of people, whose faces he had difficulty looking at. Nurses, doctors, just people. After six months of being on the streets of London avoiding people, he was finding the people in here to be oppressively present. And he couldn't run away. All of his avoidance skills, honed to perfection on the streets, now screamed inside his head, useless. He couldn't get away from them. He'd been here for six weeks, the first two in the PICU, while he was de-toxing, and the past four in this unit. Not once had he spoken. Silence was his way of keeping invisible.

Invisibility meant safety. No one made eye contact with the homeless. It made ordinary people feel uncomfortable, something that made Sherlock smirk every time someone's eyes just slid over him without registering. _Join the club_. He'd felt that way looking at everyone but a few people, all his life.

Unfortunately, here at the Priory, too many people wanted to look at him. If they weren't prodding or poking at him physically, they were talking at him. He just filtered the voices out and tuned his inner ear to other things. Right now, he was rehearsing the Bach Partita Number One. He had played it once in front of crowd of people; that had been…distracting, and the applause at the end had startled him, so he'd scuttled back to his seat in the orchestra. He also played the violin second chair that concert in Barber's Adagio for strings. He liked that experience better- the leader of the Nine was between him and the audience, which meant eyes were not on him. He preferred invisibility.

A bit like Berkelium. It was so elusive that it had taken scientists years to manufacture enough to be seen by the naked eye. _Lucky element; it gets to hide._

He started on the element's fourteen isotopes, imagining in his mind how the variations in the number of neutrons changed the element; how the addition of just one neutron could mean the difference between a half-life of 4.4 hours for Bk244, yet Bk245 had a half-life of 4.9 days. There was something awe inspiring and beautiful about that fact.

_OH!_

He stopped in the middle of the crayon stroke to grab a clean sheet of paper and started drawing on it rapidly the five lines of a stave. He scrawled cryptic notes underneath as rapidly as they occurred to him, the movement of the electrons in the sub-shells and their relation to the number of neutrons, how this would translate into quavers, minims, rests. The highest elements on the table would be the semidemihemisemiquavers, the 128th notes-so fleeting it was almost impossible to play them. Beamed notes could reflect the half-life. He started to get excited. This was really interesting- how to create a musical version of the periodic table. That would keep his brain occupied for a while. Boredom was his chief enemy in this prison.

He missed his violin terribly. It was the only regret that he'd had in the days immediately afterwards; he wished he'd taken it with him when he fled from Harrow. He could have busked, earned enough money to avoid the …other things he had to do to get the money necessary to live. Anyway, later he realised that idea was ridiculous, because busking would mean being _visible_ and that would mean Mycroft would find him. And, even if he had taken the violin, it probably would have been stolen from him by some junkie who would sell it to finance the next hit. Maybe later he would have needed the money himself more than the comfort of holding it, and playing in places where he couldn't be heard; he would have hated that- wanting what the drugs gave him more than the pleasure the violin gave him. No, it was better to have left it behind.

He continued jotting notes, and experimenting with them on the stave. He could use the different Periodic table groups as keys- the G, D and F blocks, for example, worked in both; he'd have to figure out something for S and P blocks. Would one work as C? Could Major and Minor deal in some way with isotopes? How would the new notation structure deal with decay? An element like Berkelium lasted only milliseconds. How would he be able to create a logarithmic approach to the timing of the music?

His fingers itched to hold a bow and experiment with the actual sounds in their connection to the chemical formulae, but Sherlock knew better than to ask for his violin here. They'd try to use it to extort something from him- some more "co-operation", some agreement to "participate" or "engage" with a psychiatrist or a group therapy session. To get the paper and the crayons, he'd agreed to attend such sessions. Attendance didn't mean engagement, as they discovered.

Doctor Walid was speaking. "It's time now, Sherlock. The Group is starting soon and you need to put that away."

For a second he closed his eyes. _Can't you see that this is really exciting? No one has ever tried this before. Leave me be._

But the Asian man's voice continued. "You know it was what we agreed. You get writing materials only if you attend the sessions. So come on, or we will have to take these away."

The thought of losing what he had started on was worse than having to tolerate an interruption. He put down the crayon and pushed the chair back from the desk. He ignored the doctor's encouraging smile.

As ridiculous as it was, in exchange for the paper he was willing to sit silently on a chair in a circle while other teenagers told silly stories about why they had gone off the rails. He found it amusing to think of what he might say to them. _I was never on the rails to start with. I've just reverted to type._ The first few sessions he had trouble blocking out their voices- their banal experiences just intruded and irritated him. One sixteen year old girl kept talking about her step-father kicking her out of the house when he found a joint under her bed. _Try finding someone you relied on dead in his bed._

McGarry's death had unmoored him, cut him free from what had been a brief period of stability. During his three years at Harrow, McGarry was the nucleus around which Sherlock's electrons and protons orbited. Chemistry had become his refuge, his centre of gravity. And McGarry was the one who had given him the confidence to take his interest to the next step, by telling him what he would be able to do at Cambridge.

Okay in theory, but what would happen in practice worried him all that summer before going up to Cambridge. While he relished the chance to do some really interesting chemistry at last, the thought of having to leave Harrow and go to university to do it had become increasingly oppressive. A whole new set, no- an entire _universe_ \- of new faces, useless people that he would have to negotiate, learn how to deal with. None of them knew him. He'd finally found a way to cope with Harrow and his wretched classmates, and now he was going to have to start all over again. Trinity was enormous. Bradbys House had 76 students. Trinity had nine hundred students and a hundred and fifty teaching staff. As if that wasn't bad enough, Trinity was only one of thirty one colleges. Harrow had eight hundred boys. There were fifteen _thousand_ students at Cambridge. The thought had made him terrified.

When it came to teachers, Sherlock had learned to ignore all but a handful of the masters at Harrow. But at Cambridge, he'd been torn between biochemistry and chemistry so he decided to do both; absurdly, they were in _two_ separate faculty departments, which doubled the number of academics and administration staff he'd have to deal with. None of them understood 'the care and feeding of a Sherlock.' They would expect him to behave the way they wanted real students to behave, and when he disappointed or shocked them, he would be singled out- made visible, ridiculed- and sent away as not real. It just became one huge big bang in his mind.

 _Run_. It was the one word that the voice in his head said more often than any other. Sometimes, when he looked up at the four walls of the room he was locked away in, the need to run became so strong that he thought he might scream for being confined. He'd taken to standing in front of the wall, his face inches away from it, hoping that somehow the physical impossibility of escape would suppress the biological urge to flee.

It was worse, far worse that the physical symptoms of withdrawal. As disgusting and painful as they had been, at least they didn't last long. But the craving for anything to stop his panic now was strong enough for him to agree to take the antidepressants. They didn't work half as effectively as the drugs he'd been able to source on the streets, but his taking them seemed to loosen up the wariness of the staff. They started negotiating.

A nod or a shake of his head was all he would give them. He wouldn't speak. As he had at each of the previous group therapy sessions, the psychiatrist in charge now turned to him and asked, "Do you have anything to say, Sherlock? Perhaps something about yourself, or a comment on something on what someone else has said?" He shook his head.

Then it was over, and he was being escorted back to his room. As the attendant used the swipe card on the lanyard around his neck to open the electronic lock on his door, Sherlock could hear voices inside. _Doctor Cohen._

She had spread out all of the papers on his bed. She looked up when he came in, and smiled. "This is really interesting, Sherlock. I've explained to Doctor Walid your interest in the Periodic Table. Why did Number 97 trigger something different?"

The Asian doctor was looking confused. "97? The Bk on your sheets- it's Berkelium?" But he pronounced it wrong, sounding the "e" out so it became four syllables. Without thinking, Sherlock corrected him. "It's _Burklium_ , like the university." As soon as the words escaped, he knew what he had done. Too late.

Esther smiled, and then whispered, "Welcome back, Sherlock. We've missed you."

The moment teetered. He could run for cover again and retreat into silence. But then she asked the one thing that made him decide against that. She pulled the last sheet out- the one with the stave on it. "Now tell me what's going on with this notation. Can you really make a _musical_ Periodic Table?"

He made a choice, and started to explain.

**Author's Note:**

> Author's Note: This story is written in recognition of the fact that every day children go missing. Some do it on purpose to avoid a life that is proving to be too difficult to live. For young people, life on the streets can be a chance to "re-boot" their lives. 
> 
> * See my story Ex Files, Chapter 29, Expedition, over on Fan Fiction
> 
> ** Why Mycroft worries about FS Ford is covered in Ex Files, Chapter 38, Extrapolate, again over on Fan Fiction.


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